At present, IPTV is commercially applied to the global market in a large scale. A Set Top Box (STB) is a generic term for client devices (also referred to as terminals) which provide content services for users. The STB may be embodied as various types of devices or terminals, including traditional devices connected with display devices, such as Personal Computer (PC) or an STB, or user devices installed with multimedia service programs, such as smart phone or Pad. That is, the STB may refer to any type of terminal or device which provides users with multimedia services (sometimes referred to as content service). Content, in this context, could mean any or all of video, audio, Internet web pages, interactive video games, or other possibilities. When services of an IPTV service system become inaccessible due to the upgrading, server failure or network failure, a Set Top Box (STB, or user device or terminal) cannot provide normal TV service for a user. Since the IPTV service is a telecommunication level service, if the services of the IPTV service system become inaccessible, a large scale of users may be greatly influenced. Moreover, a TV service, as the most important recreational activity for ordinary family life particularly in holidays, may be more greatly influenced.
For the above problem in a related technology, there is yet no effective solution.